Field of the Disclosure
Certain aspects of the present disclosure generally relate to removing fouling entities from marine equipment, and, more particularly, to laser-removal of barnacle larvae and barnacles from sensor streamers.
Description of Related Art
Marine seismic surveys are one type of marine geophysical survey which utilizes sound waves transmitted to the earth's crust and reflected back to recording sensors. The recording sensors may be hydrophones or other sensors in one of a number of towing assemblies, commonly called streamers or sensor streamers, that may be towed behind a survey boat. When towed behind the survey boat, the streamers may be submerged. A sound, or other energy, source may also be towed in the water behind the survey boat for transmitting energy to be received by the receivers of the streamers. One common application of marine geophysical surveying is oil and gas exploration in marine environments. More particularly, sound waves received during a marine seismic survey may be analyzed to locate hydrocarbon bearing geological structures, and thus determine where deposits of oil and natural gas may be located. In a similar fashion, marine electromagnetic (EM) surveys may be conducted using EM energy transmitted by a submerged source and detected by EM receivers.
Periodically, cleaning operations may be conducted on streamers used in marine seismic surveys. Cleaning operations may be conducted by a crew on a workboat separate from the survey boat. To clean a particular one of the towed streamers, the workboat crew may lift the streamer out of the water, clean by hand, and lower the streamer back into the water. Since the streamers can have significant length, (e.g., 8 km), in some cases only a portion of the streamer is lifted out of the water. The workboat crew may progressively lift portions of a particular streamer out of the water until cleaning is complete. The workboat crew may then progress to the next streamer and repeat the process. The process may be subsequently repeated until all streamers have been cleaned. The process of cleaning using a workboat crew can be very time consuming, and in some cases, dangerous to the crew members that perform the work.
Remotely operated vehicles (ROVs) may be useful for supporting marine geophysical surveying. For example, an ROV may be deployed to maintain (e.g., clean, repair) a streamer towed behind a survey boat, allowing maintenance of a streamer without reeling the streamer back onto the survey boat. ROVs may also be used for other tasks in marine exploration, such as placing equipment on the seabed.
Lifting a streamer out of the water may prevent the streamer from collecting survey data, thus interfering with survey operations. Cleaning operations may also be conducted on streamers with a streamer cleaning unit (SCU) that cleans a streamer while it is submerged. A streamer cleaning unit may be attached to a streamer and clean the streamer with brushes and other tools to physically remove obstructions from the streamer. The use of brushes and other tools on the streamers produces sounds or other noise that can interfere with collecting survey data. Similarly, the presence of metal parts of an SCU in close proximity to a streamer may interfere with collection of EM survey data. It is therefore desirable to clean streamers by methods that produce less sound interference and EM interference to improve the collection of survey data.